java新手筆記9

標籤：

1.bank類

package com.yfs.javase;//類封裝public class BankCard {//屬性int balance;//預設0  執行個體變數 分配給每個對象一個//String name; // 方法 存錢public void saveMoney(int   money) {if(money < 0) {System.out.println("非法操作...");return;}System.out.println("向賬戶存入" + money +"元...");balance += money;}    //取錢  調用時傳入參數public void drawMoney(int money) {//驗證餘額if(balance < money) {System.out.println("賬戶餘額不足...");return; //終止方法調用} System.out.println("從賬戶取出" + money + "元..."); balance -= money;}}

 2.測試

package com.yfs.javase;public class CardTest {public static void main(String[] args) {//  BankCard bc1 = null;//聲明引用//  bc1 = new BankCard();//建立對象  BankCard bc1 = new BankCard();  System.out.println("銀行卡餘額：" + bc1.balance);  bc1.drawMoney(200);//調用對象方法    bc1.saveMoney(5000);    bc1.drawMoney(500000);    bc1.drawMoney(500);    bc1.saveMoney(-500);  System.out.println("銀行卡餘額：" + bc1.balance);  }}

 3.測試1

package com.yfs.javase;public class CardTest2 {public static void main(String[] args) {  BankCard bc1 = new BankCard();  System.out.println("銀行卡餘額：" + bc1.balance);  bc1.saveMoney(5000);  bc1.drawMoney(500);  System.out.println("銀行卡餘額：" + bc1.balance);    BankCard bc2 = new BankCard();  System.out.println("銀行卡餘額：" + bc2.balance);  bc2.saveMoney(3000);  System.out.println("bc2銀行卡餘額：" + bc2.balance);  System.out.println("bc1銀行卡餘額：" + bc1.balance);    }}

 4.測試2

package com.yfs.javase;public class CardTest3 {public static void main(String[] args) {  BankCard bc1 = new BankCard();  bc1.saveMoney(5000);  bc1.drawMoney(500);  System.out.println("銀行卡餘額：" + bc1.balance);    BankCard bc2 = new BankCard();  bc2.saveMoney(3000);  System.out.println("bc2銀行卡餘額：" + bc2.balance);  bc2.drawMoney(5000);  bc2.balance = 10000;//修改餘額  不安全操作  bc2.drawMoney(5000);  System.out.println("bc2銀行卡餘額：" + bc2.balance);    }}

 1.1bank類

package com.yfs.javase.update;//類封裝public class BankCard {//屬性  private 屬性私人  只能在當前類中訪問private int balance;// 執行個體變數 分配給每個對象一個private int password;// 方法 存錢public void saveMoney(int   money) {if(money < 0) {System.out.println("非法操作...");return;}System.out.println("向賬戶存入" + money +"元...");balance += money;//在方法中訪問}    //取錢  調用時傳入參數public void drawMoney(int money) {//驗證餘額if(balance < money) {System.out.println("賬戶餘額不足...");return; //終止方法調用} System.out.println("從賬戶取出" + money + "元..."); balance -= money;}//通過訪問balance屬性方法 不能修改public void  getBalance () {System.out.println("賬戶餘額：" + balance);}}

 2.1測試

package com.yfs.javase.update;public class CardTest3 {public static void main(String[] args) {  BankCard bc1 = new BankCard();  bc1.saveMoney(5000);  bc1.drawMoney(50000);//  bc1.balance = 100000000;//編譯出錯//  System.out.println("銀行卡餘額：" + bc1.balance);//私人屬性不能訪問   bc1.getBalance(); // bc1.password;  }}

 3.1方法重載條件

package com.yfs.javase.update;import java.util.Random;public class Demo2 {//public int add(int a, int b) {//return a + b;//}    //變數名稱不能成為重載條件//public int add(int c , int d) {//return c + d;//}public double add(int a , double b) {return a + b;}//傳回值類型不能成為重載條件public long add( int a, int b) {return a + b;}public static void main(String[] args) {Demo2 d1 = new Demo2();long val = d1.add(1,6);}}

 4.1方法重載樣本

package com.yfs.javase.update;public class OverRideDemo {//方法的重載  方法使用相同的名字public int add (int a, int b) { return a + b;}    public  int  add (int a , int b, int c) {return a + b + c;}public double add( double a, double b) {return a + b;}public static void main(String[] args) {//建立對象OverRideDemo od = new OverRideDemo();int val = od.add(3,5);System.out.println("add(3,5) = " + val);val = od.add(3,5,8);//根據調用時傳入參數個數 類型匹配對應方法System.out.println("add1(3,5,8) = " + val);double result = od.add(3.14, 2.71);System.out.println("add(3.14, 2.71) = " + result);}}

 

java新手筆記9